Powdered Sugar Or Cornstarch

I think I read somewhere, if you roll out your fondant using cornstarch, it tends to dry out the fondant and is more likely to crack. Is that right, should I use powdered sugar instead? Also, I recently made chocolate fondant, because I didn't want any white residue, I used the "mat". I really hate that thing. It makes the fondant feel greasy, and when you go to smooth it out with your smoother, the smoother tends to stick to the fondant. So, how do I roll out chocolate fondant, or any dark color fondant, and not have white residue? IfI use vodka to get it off, does it not leave shiny spots? Same for the shortening? Would appreciate some help please!

Second, when using the mat I often smooth on a small amount of powdered sugar after the fondant is applied to the cake. This immediately removes the stickiness and is fast enough that you can still smooth the fondant.

Third, regarding dark fondant, I apply it and then rub it with my hands as I am smoothing it. All the powdered sugar comes off. If some still remains I lightly brush it. If that still does not do what I need you can lightly steam it. HTH